Listed as an exploit. This can effectively make duplicant not require any oxygen whatsoever.
Small note that duplicants "Recovering breath" do consume oxygen under normal circumstances (not wearing an atmo suit).
Steps to Reproduce
Give an Atmo Suit to a duplicant and let it run out of oxygen. At this point the duplicant will need to recover its breath but wont consume any oxygen when doing so.
This issue has not been confirmed by a developer yet.